This interesting article covers many of the unorthodox uses of duct tape, detailing some of its life-saving applications in medicine, outer space, the outdoors, etc. One funny tidbit:

Of course, for all its versatility, perhaps the most interesting thing about duct tape is also the most ironic: It’s lousy for use on ducts.

In 1998, Lawrence Berkeley National Laboratory physicists Max Sherman and Lain Walker tested a variety of sealing materials on sheet metal ducting, then heated and cooled the ducts to simulate the aging process. They soon found that duct tape leaked air so badly much of the cooling and heating was wasted — and that the tape frequently shrunk, dried up or separated.